(AP) -- Actor and comedian Tracy Morgan and two members of his entourage were in critical condition Sunday, a day after a tractor-trailer rammed into his chauffeured limousine bus, setting off a deadly chain-reaction pileup.

The former "Saturday Night Live" and "30 Rock" cast member was returning from a standup show in Delaware early Saturday with six others when the limo bus overturned on the New Jersey Turnpike near Cranberry Township, killing Morgan's mentor and fellow comedian James "Jimmy Mack" McNair. A Wal-Mart truck driver was charged with death by auto and four counts of assault by auto.

Jeffrey Millea, of Shelton, Connecticut, and comedian Ardie Fuqua Jr. were listed in critical condition along with Morgan at Robert Wood Johnson Hospital, hospital spokeswoman Zenaida Mendez said Sunday. Another comedian, Harris Stanton, was treated and released from the hospital Saturday.

The truck driver, 35-year-old Kevin Roper, of Jonesboro, Georgia, apparently failed to slow for traffic ahead and swerved at the last minute to avoid a crash, the Middlesex County Prosecutor's office said.

Instead, the big rig smashed into the back of the Mercedes limo bus, prompting a chain-reaction crash with a second tractor-trailer, an SUV and two cars, authorities said. No one in the other vehicles was injured.

Roper, accompanied by his attorney, turned himself in to state police. He was released on $50,000 bail Saturday night, Wal-Mart spokesman David Tovar said Sunday.

Wal-Mart President Bill Simon said in a statement that the company "will take full responsibility" if authorities determine its truck caused the accident.

The National Transportation Safety Board said it was working with state police to look at any issues in the crash related to commercial trucking and limousine safety.

Morgan's limo was owned by Atlantic Transportation Services, which said it had one employee behind the wheel and a second in the front passenger seat. Neither was injured.

"Although the investigation is still pending, we concur with the preliminary reports that the accident was caused by another vehicle traveling behind the Atlantic limo bus," the Rehoboth Beach, Delaware-based company said.

Fuqua had tweeted that he was opening for Morgan on Friday night at Dover Downs Hotel & Casino in Delaware. On his Instagram page, Fuqua included a collage of photos from the show.

"This is what it looks like from the stage to see a standing ovation from 1500 people," Fuqua wrote at around midnight Friday. "Then we traveled back to NYC in style in a luxury Mercedes Sprinter. Road life is a good life!"

McNair, 62, of Peekskill, New York, was a close friend and mentor to Morgan, Morgan's ex-wife, Sabina Morgan, told the New York Daily News. "He was one of the first comedians that took Tracy under his wing," she said. "They were very close."

Royale Watkins, a Los Angeles-based comedian who said he had performed in New York clubs with Morgan and McNair, described McNair as having a big personality.

"There may be guys like Tracy who get the fame and notoriety, but you have people like Jimmy Mack who have kind of energized and fueled cats like Tracy and kept them going on the road," Watkins said.

Morgan, a New York City native, joined "SNL" in 1996 and left to star in "The Tracy Morgan Show" in 2003. That show lasted just one season. In 2006, Morgan found a long-running role on NBC's hit show "30 Rock," which was created by "SNL" co-star Tina Fey. He received an Emmy nomination for best supporting actor for "30 Rock" in 2009.

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Associated Press writer Bob Lentz in Philadelphia contributed to this report.